1. Field of the Invention:
The invention relates to underground houses and methods of construction thereof and, more particularly, to dome-shaped underground houses and methods of construction thereof.
2. Description of the Prior Art:
With the advent of rapidly rising housing construction costs and heating and cooling costs, many different types of low-cost energy-efficient dwelling structures have been proposed. Underground or partially underground dwelling structures which have been proposed have certain advantages, a major advantage being that the temperature of the earth becomes more nearly constant as depth of the dwelling structure increases. Consequently, relatively uniform temperatures both in summer and winter have been obtained with previous underground or partially underground dwellings. However, in the past, it has been difficult and expensive to attain satisfactory lighting of the interior of known underground structures. Further, the costs of construction frequently have been unacceptably high compared to other low cost above-ground (but less energy efficient) dwelling structures.
Accordingly, it is an object of the invention to provide a low cost, energy-efficient dwelling structure and method of construction thereof providing substantially more natural interior lighting than has been available from previous underground or partially underground dwelling structures.
A variety of above-ground dome-shaped building structures have been proposed. However, they have required complex and unduly expensive welded steel frames. Expensive siding materials have been attached to the steel frames. Due to their high cost and the absence of any advantages related to energy efficiency, above-ground dome-shaped residential structures have not been popular.
None of the previously known above ground, underground or partially underground dome-shaped or "barrel-shaped" building structures have been both relatively low in cost and easily assembleable by untrained "do-it-yourselfers". For example, U.S. Pat. No. 2,365,145 discloses above-ground dome-shaped and barrel shaped structures constructed of preformed vertical arch members. The disclosed structure includes numerous horizontal channel members attached to the vertical arch members. Metal lathing is attached by wires to the inner surfaces of the vertical arch members to cover the interior surface of the erected structure, and plaster is ultimately applied to the metal lathing. On the outside of the grid formed by the vertical arch members and the horizontal channels attached thereto a blanket of insulation material disposed between sheets of paper is secured by tie wires to the vertical arch members. A layer of mesh is then applied over the blanket of insulation, and the exterior of the framework is shot with shotcrete. This structure and technique has numerous shortcomings. It would take a high degree of quality control and precision in providing accurately drilled bolt holes which would be properly aligned so that a "do-it-yourselfer" could make the many connections required between the vertical arch channels and the horizontal channels. The structure requires a very large number of both vertical arch channel members and horizontal channel members, as these are required to support the insulation layer without undue sagging when the wet shotcrete is sprayed on it. The large number of vertical arch supports and horizontal channel supports requires a very large number of bolt connections (or, if bolts are not used, then welded connections would be required and would greatly increase the cost.) The labor required for attaching the metal lathing to the interior of the vertical arch channels would be excessive, as would the cost of the metal lathing itself. Furthermore, this would provide very little support for the insulation, which subsequently is loaded with wet shotcrete. From a practical viewpoint, paperbacked fiberglass insulation or the like could not be used, because it would not adequately support the weight of subsequently applied wet gunnite or shotcrete without undue sagging. In fact, it is more than likely that shotcrete or gunnite sprayed at high pressure at the surface of the insulation would simply blow right through it.
Furthermore, even if the gunnite or shotcrete is applied in very thin layers which are each allowed to dry before a subsequent layer is sprayed thereon or otherwise allowed, the structure shown in U.S. Pat. No. 2,365,145 would be highly impractical for underground structures because unless waterproof, rigid insulation were used, there would be a great build up of condensation in the insulation layer, which would cause it to deteriorate and would also cause rusting and deterioration of the steel frame. Over a twenty or thirty year period, such rusting could dangerously weaken the structure.
U.S. Pat. No. 4,144,680 discloses an above-ground dome-shaped structure in which spaced vertical tubular arch members extend upward from a foundation. Pairs of clamped together tubular members are bolted to the vertical arch members to circumscribe the inner and outer wall structure. The space between the two horizontal members of each pair is a dead space. Separate inside and outside wall structures are provided on the inner and outer sides of the vertical arch members. Each wall structure includes an inner layer of mesh, several layers of horizontal and vertical reinforcing rod, a second layer of mesh and concrete which is applied to surround the mesh layers and reinforcing rod layers. This structure would not be very satisfactory for applying shotcrete, because much of it would tend to pass through the mesh layers and be wasted. Furthermore, the dead space would result in serious water condensation problems unless the concrete in both the inner and outer reinforced walls is adequately waterproofed. The provision of duplicate inner and outer walls would greatly increase the expense of the structure, and the complexity of making all of the bolted, clamped connections of horizontal tubular members to the vertical tubular members is impractical because it is extremely labor intensive. The structure is completely unsuitable for an underground structure that could be partially erected by a do-it-yourselfer. There is nothing in the design of either of the above disclosed structures or the structure disclosed in U.S. Pat. No. 4,155,967 which facilitates expandability and making of either elongated dome-shaped structures, barrel-shaped structures, or even composite structures.
It is another object of the invention to provide a dome-shaped structure having sufficient structural strength to support surrounding earth and earth which lies against the structure without requiring complex and unduly expensive supporting structure.
Previously, dome-shaped structures having exterior concrete or gunnite surfaces were required to be constructed by utilizing preformed dome-shaped forms or support structures to prevent sagging of the moist concrete walls prior to hardening thereof. The necessity for providing such forms added greatly to the difficulty and expense of making prior dome-shaped building structures.
Accordingly, it is still another object of the invention to provide a method of making a dome-shaped building structure without the necessity of providing expensive forms to support its concrete wall when it is moist.
It is another object of the invention to provide a method of making dome-shaped and barrel-shaped building structures which can be substantially erected by unskilled do-it-yourselfers.
It is another object of the invention to provide at least partially underground building and method of construction which does not require an excessive number of vertical arch members and heavy horizontal members which must be bolted or welded to the vertical arch members.
It is another object of the invention to provide an underground structure and method of building which allows a layer of shotcrete to be applied in full thickness in a single application without the need for waiting for sublayers thereof to dry.
It is another object of the invention to provide at least a partially underground arched structure and method for making which requires a reduced thickness for an internal layer of plaster to provide an attractive, durable interior surface that has very little tendency to crack or break loose and fall.
It is another object of the invention to provide at least a partially underground structure and method of building which avoids the problem of excessive condensation caused by passage of vapor from overylying soil into the structure where corrosion of the steel structural members can occur and wherein staining of the interior surface of the structure due to leakage of moisture can occur.